1. Technical Field
The present invention relates to a head cleaning method and a liquid discharging apparatus.
2. Related Art
An example of a liquid discharging apparatus is an ink jet printer (hereinafter, printer) in which ink (liquid) is discharged from a nozzle provided in a head. In the printer, since foreign matter such as ink, paper dust or the like adheres to a nozzle opening surface of the head, a wiping operation is regularly carried out in which the foreign matter is wiped off from the nozzle opening surface by a wiper. When ink adheres to the nozzle opening surface for a long time, the ink thickens and solidifies and thus, is not completely wiped off by only the wiper. Accordingly, a method is proposed in which the wiping operation is carried out when the nozzle discharges ink. In this way, the thickened and solidified ink can be dissolved and wiped off by the wiper wet with the ink. Thereafter, when the wiping operation is carried out again without the ink being discharged from the nozzle (a dry wiping operation is carried out), it is possible to more thoroughly clean the nozzle opening surface (refer to JP-A-2006-212863).
However, when the wiping operation is carried out, there is a case where ink in the nozzle is guided by the ink adhering to the wiper and is drawn out by the wiper. For this reason, in a case where the wiping operation is carried out without the ink being discharged from the nozzle, when a pressure applied to the ink in the head is low, the nozzle from which the ink is drawn out by the wiper cannot be replenished with the ink. As a result, air bubbles remain in the nozzle, and a discharge failure occurs. In contrast, when a pressure applied to the ink in the head increases in such a manner that the nozzle is replenished with the ink after the ink is drawn out from the nozzle by the wiper, the ink cannot be discharged from the nozzle during printing, and a discharge failure occurs.